The present invention relates to an electromagnetic contactor carrying out switching of a current supplied to an electric load device such an electric motor and particularly to an electromagnetic contactor having a DC electromagnet with a nonmagnetic structural component mounted between a movable core and a stationary core.
An electromagnetic contactor is a device with a stationary core, a movable core arranged opposite to the stationary core and a coil arranged around the periphery of a main leg of the stationary core contained in an insulating case. With the coil excited to attract the movable core to the stationary core, a movable contact and a stationary contact are electrically connected. In an electromagnetic contactor having a DC electromagnet with a nonmagnetic structural component mounted between a movable core and a stationary core, as disclosed in JP-A-10-188765, the nonmagnetic structural component is attached to the bottom end surface of the movable core opposite to the top end surface of the stationary core for preventing the movable core from being attracted to the stationary core by residual magnetism due to magnetization retained in the stationary core even after the excitation of the coil is stopped.
The nonmagnetic structural component attached to the bottom end surface of the movable core disclosed in JP-A-10-188765 is shown in FIGS. 7A to 7C. FIG. 7A is a perspective view showing a nonmagnetic plate 2 as the nonmagnetic structural component integrally provided with a covering part 2a covering the whole bottom surface of the movable core 1 and two engaging parts 2b each engaging with the upper part of the movable core 1. FIG. 7B is a perspective view showing a nonmagnetic plate 3 as the nonmagnetic structural component in the shape of a frame surrounding the peripheral side face of the movable core 1. The movable core 1 and the nonmagnetic plate 3 are held between cushioning springs 4 each disposed on the top face of the movable core 1 and a coupling pin 6 arranged across the bottom face of the movable core 1. FIG. 7C is a perspective view showing a nonmagnetic plate 5 as the nonmagnetic structural component in the shape of a flat plate stuck onto the bottom face of the movable core 1 by an insulating adhesive.
[Patent Document 1] JP-A-10-188765
However, the electromagnetic contactor provided with each of the nonmagnetic plates 2, 3 and 5 disclosed in JP-A-10-188765 has a problem in a product cost. Namely, each of the nonmagnetic plates 2 and 3 shown in FIGS. 7A and 7B, respectively, is a structural component with a shape more complicated compared with the shape of the nonmagnetic plate 5 shown in FIG. 7C provided as a flat plate structural component to cause a high component unit price, by which there is a possibility of increasing the product cost of the electromagnetic contactor.
Moreover, the nonmagnetic plate 5 shown in FIG. 7C takes much time in sticking it onto the movable core 1 by using an adhesive to increase labor cost, which will cause possible increase in the product cost of the electromagnetic contactor.
Accordingly, it is an object of the invention to prepare a nonmagnetic structural component with a simple shape and also reduce the labor cost in attaching the nonmagnetic structural component onto the bottom face of a movable core to thereby provide an electromagnetic contactor in which the product cost can be made reduced.
Further objects and advantages of the invention will be apparent from the following description of the invention.